Antireflection films are generally arranged in the outermost surface of displays in image displays such as cathode ray tube (CRT), plasma display (PDP), electroluminescence display (ELD), and liquid crystal display (LCD) so as to reduce reflectance by utilizing the principle of optical interference for the purpose of preventing contrast reduction and mirroring of images by the reflection of outer light.
These antireflection films can be manufactured by forming on a support a low refractive index layer having a refractive index lower than that of the support and of an appropriate thickness. From the viewpoint of realizing low reflectance, materials having the lowest possible refractive index are desired for a low refractive index layer. Since an antireflection film is used on the outermost surface of a display, the film is required to have high scratch resistance. For realizing high scratch resistance in a thin film of a thickness of 100 nm or so, the strength of the film itself and adhesion property to the lower layer are required.
For reducing the refractive index of materials, means of (1) introducing a fluorine atom, and (2) reducing the density (introduction of voids) are used, but film strength and interfacial adhesion decrease and scratch resistance lowers in both of these means, so that the compatibility of low refractive index with high scratch resistance has been a difficult problem. It is important to sufficiently advance curing reaction to realize high scratch resistance. From the viewpoint of productivity, it is advantageous to coat a fluorine-containing polymer on a support and then cure the coated film by any means. Methods of reacting the hydroxyl group of a fluorine-containing polymer and a curing agent with an acid catalyst to cure the low refractive index layer of an antireflection film are disclosed in JP-A-11-228631, JP-A-2003-36732 and JP-A-2004-307524.
On the other hand, curable compositions and coatings using amine salts of sulfonic acids as the catalysts are proposed in JP-A-62-174276, JP-A-1-259071, JP-A-2-173172 and JP-A-2-302477.
In the techniques of JP-A-11-228631, JP-A-2003-36732 and JP-A-2004-307524, sulfonic acids and carboxylic acids are used as the acid catalysts. Curing activity is certainly high according to these techniques, but a curing reaction partly proceeds during preservation, so that the stability of the coating solution is insufficient and coating conditions are limited. Therefore, the compatibility of curing activity and the stability of a coating solution has been desired.